1. Field of the Invention
This invention relates generally to optical communication networks and, more particularly, to methods and systems for distributing equipment associated with optical communication systems.
2. Description of Related Art
Recently, optical communications have become established as a next generation communication technology. Advances in optical fibers that carry optical data signals, and in techniques (e.g., wavelength division multiplexing (WDM)) for efficiently using the available bandwidth of such fibers, have caused optical technologies to be utilized in state-of-the-art long haul communication systems. As used herein, “WDM” may include either or both of the functions of multiplexing (i.e., multiple signals into one signal) and demultiplexing (i.e., one signal into multiple signals).
Depending upon the relative locations of the data source and the intended recipient, optical data signals may traverse different optical communication systems between the two locations. On example of this occurs in trans-oceanic (e.g., trans-Atlantic) data connections. For example, optical signals may travel along both a terrestrial optical communication system and a submarine optical communication system.
FIG. 1 is a schematic diagram of an exemplary optical communication system 100 that includes an undersea, or submarine, portion. The optical communication system 100 may include two land-based, or terrestrial, WDM terminals 110 and 140 that are connected by a submarine optical fiber 120, perhaps in the form of an undersea cable. The submarine optical fiber 120 may connect to one or more line units 130 that are used to amplify the optical signal in the fiber 120. Line units 130 are also sometimes referred to as “repeaters.” Although communication may be shown in one direction in FIG. 1 and elsewhere herein, those skilled in the art will appreciate that communication may be bi-directional, for example by using a pair of optical fibers or other known methods of bi-directional optical communication.
For “long haul” (e.g., greater than or equal to several hundred kilometers) optical communications, the optical signal may be periodically amplified to compensate for attenuation in the fiber 120. As many line units 130 are used as necessary to amplify the transmitted signal so that it arrives at WDM terminal 140 with sufficient signal strength (and quality) to be successfully detected and transformed back into a terrestrial optical signal. The terminals 110 and 140 may contain all of the components needed to process the terrestrial optical signals to and from submarine optical signals.
FIG. 2 is a block diagram of an exemplary terminal unit 110 of the optical communication system 100. The terminal unit 110 may include long reach transmitters/receivers (LRTRs) 210, WDM and optical conditioning equipment 220, link monitor equipment 230, line current equipment 240, a backplane 250, and a network management system 260. All of this equipment has typically been housed in one or more cabinets (not shown) disposed at a cable landing site (also referred to as a cable landing station, or merely “cable station”) near the point at which the undersea cable 120 exits the submarine optical communication system.
The LRTRs 210 may be configured to convert terrestrial optical signals into an optical format suitable for long haul transmission. The LRTRs 210 also may be configured to convert the undersea optical signal back into its original terrestrial format and provide forward error correction for the submarine line. The WDM and optical conditioning unit 220 may be configured to multiplex and amplify the optical signals in preparation for their transmission over cable 120 in a transmitting direction. In the opposite (i.e., receiving) direction, the WDM and optical conditioning unit 220 may demultiplex optical signals received from cable 120. The link monitor equipment 230 may be configured to monitor the undersea optical signals and undersea equipment for proper operation. The line current equipment 240, which may also be referred to as power feed equipment (PFE), provides power to, for example, the undersea line units 130 coupled to the undersea cable 120.
As these optical systems are upgraded and/or new submarine optical communication systems are deployed, the number of channels and number of optical fibers associated with each system may increase dramatically. Retrofitting existing cable landing stations to handle new equipment may not be commercially feasible. At the same time, acquiring new landing sites may be equally challenging.
Thus, there is a need in the art to expand information capacity by modifying or adding equipment, while minimizing access to cable landing stations and space usage therein.